My project explored the impact of temperature and annealing on the optical constants of La0.67Sr0.33MnO3 (LSMO) films grown on a lanthanum aluminate (LAO) substrate. This was done with infrared and optical spectroscopy, which allows us to measure the complex dielectric function of the material. Both the substrate and the film-substrate system have been modeled in order to closely examine the properties of annealed and unannealed LSMO. The Jahn-Teller energy splitting was measured, and an additional feature in the unannealed film conductivity allowed the Hund's coupling energy to be deduced directly.